Safety Warning on Clobazam
On December 3, 2013, the US Food and Drug Administration (FDA) issued a drug safety communication warning of "rare but serious" skin reactions from the antiseizure drug clobazam. These included Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN).
Clobazam received FDA approval for the add-on treatment of seizures associated with Lennox-Gastaut syndrome in adults and children aged 2 years or older on October 21, 2011. Clobazam was the subject of a recent Epilepsy Notes.
Life-Threatening Skin Reactions
The FDA identified 20 cases of SJS and TEN associated with clobazam from its Adverse Event Reporting System (AERS) database. A single additional case came from the literature.
Approximately 31,000 patients have received clobazam since its approval in 2011, which suggests a rate of at least 20 cases per 31,000 users, or 6 cases per 10,000 users. Because not all cases may have been reported to the FDA, this calculation probably represents an underestimate.
Two deaths occurred, one of which was "possibly" related to clobazam. One case resulted in blindness, and all required hospitalization. Although nearly all patients (19 of 20) had taken other drugs associated with SJS or TEN, such as antiepileptic drugs (n = 18), antibiotics (n = 3), or sulfasalazine (n = 2), a strong temporal relationship (within 2 months) for 14 of the 17 cases that had timing information strongly implicated clobazam. One patient developed TEN with clobazam monotherapy.
Many patients improved after clobazam was stopped. The FDA advised that patients taking clobazam should seek immediate medical treatment and talk to their healthcare professionals if they develop rashes, blistering or peeling of the skin, mouth sores, or hives.